1. Field of the Invention
The present invention relates to a lubricant supplying device, and an image forming apparatus.
2. Description of the Related Art
Widely known are image forming apparatuses, such as printers, facsimiles, and copying machines, including a lubricant supplying device that supplies a lubricant to the surface of an image carrier to protect and reduce friction on the image carrier, such as a photosensitive element and an intermediate transfer belt serving as a target to be supplied with the lubricant.
The lubricant supplying device includes a supplying member that comes into contact with a bar-shaped solid lubricant and supplies a finely powdered lubricant scraped off by rubbing the solid lubricant to the image carrier. The lubricant supplying device further includes a lubricant holding member that holds a portion of the solid lubricant on the side opposite to the side coming into contact with the supplying member. The lubricant holding member is housed in a case of the lubricant supplying device in a manner movable in directions in which the solid lubricant comes into contact with and is separated from the supplying member. Furthermore, a pressing mechanism that presses a portion of the lubricant holding member on the side opposite to the solid lubricant holding side toward the supplying member is provided to a space on the side opposite to the solid lubricant holding side of the lubricant holding member in the case.
When the supplying member rotates, the solid lubricant in contact therewith is rubbed, and a lubricant scraped off from the solid lubricant and adhering to the supplying member is applied on the surface of the image carrier. As the solid lubricant is rubbed and gradually scraped by the supplying member, the lubricant holding member moves toward the supplying member. As a result, the solid lubricant is brought into contact with the supplying member from the early period to the last period, whereby the supplying member can scrape the solid lubricant reliably.
If an image forming operation is performed in a state where the lubricant runs out, no protective effect of the lubricant is exerted, thereby abrading and deteriorating the image carrier. Japanese Patent Application Laid-open No. 2010-271665 and Japanese Patent Application Laid-open No. 2011-197126 disclose lubricant supplying devices including a residual amount detecting unit. The residual amount detecting unit detects that there is only a small amount of a lubricant left by detecting that the length of a solid lubricant in a direction in which the solid lubricant moves while being scraped by the supplying member (hereinafter, referred to as the height of the solid lubricant) is equal to or smaller than a predetermined value.
The lubricant supplying devices disclosed in Japanese Patent Application Laid-open No. 2010-271665 and Japanese Patent Application Laid-open No. 2011-197126 include a lubricant holding member formed of a conductive member and an electrode member coming into contact with the conductive lubricant holding member. In the residual amount detecting unit disclosed in Japanese Patent Application Laid-open No. 2010-271665 and the sixth modification of Japanese Patent Application Laid-open No. 2011-197126, the conductive member and the lubricant holding member come into contact with each other to establish electrical continuity therebetween at the early period of use. If the height of the solid lubricant decreases and there is only a small amount of the lubricant left, the conductive member and the lubricant holding member are separated from each other to break the electrical continuity therebetween. Shifting from electrical continuity to electrical discontinuity in this manner enables the residual amount detecting unit to detect that there is only a small amount of the lubricant left.
By contrast, in the residual amount detecting unit disclosed in the fifth modification of Japanese Patent Application Laid-open No. 2011-197126, the conductive member and the lubricant holding member are separated from each other and do not establish electrical continuity therebetween at the early period of use. If the height of the solid lubricant decreases to equal to or smaller than the predetermined value, the conductive member and the lubricant holding member come into contact with each other to establish electrical continuity therebetween. Shifting from electrical discontinuity to electrical continuity in this manner enables the residual amount detecting unit to detect that there is only a small amount of the lubricant left.
In the residual amount detecting units disclosed in Japanese Patent Application Laid-open No. 2010-271665 and Japanese Patent Application Laid-open No. 2011-197126, an assembly error of the electrode member, for example, makes it difficult to detect a state just before the solid lubricant runs out (an end state). Therefore, the residual amount detecting units detect a state prior to the end state (a near-end state). As a result, the lubricant is not used up completely, and a part of the lubricant is wasted.
The present applicant is developing a lubricant supplying device including a lubricant end determining unit that measures the amount of lubricant applying operation, such as the number of sheets on which images are formed and the rotating distance (rotation rate) of the supplying member, after the residual detecting unit detects the near-end state and determines that the lubricant is in the end state when the amount of lubricant applying operation reaches a predetermined value. The lubricant supplying device can suppress waste of the lubricant.
The lubricant supplying device under development, however, has a defect in that the lubricant runs out before the amount of lubricant applying operation reaches the predetermined value. As a result of deliberate research on the defect, the present inventers found the following: the solid lubricant is readily scraped under a low-temperature environment and a low-humidity environment, and the solid lubricant decreases more quickly under the low-temperature environment and the low-humidity environment than under the normal environment.
In view of the problems described above, there is needed to provide a lubricant supplying device, and an image forming apparatus that can suppress waste of a lubricant and prevent operations of the device when the lubricant runs out.